1 /* $NetBSD: auth.c,v 1.20 2017/10/07 19:39:19 christos Exp $ */ 2 /* $OpenBSD: auth.c,v 1.124 2017/09/12 06:32:07 djm Exp $ */ 3 /* 4 * Copyright (c) 2000 Markus Friedl. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 __RCSID("$NetBSD: auth.c,v 1.20 2017/10/07 19:39:19 christos Exp $"); 29 #include <sys/types.h> 30 #include <sys/stat.h> 31 #include <sys/socket.h> 32 33 #include <errno.h> 34 #include <fcntl.h> 35 #include <login_cap.h> 36 #include <paths.h> 37 #include <pwd.h> 38 #include <stdarg.h> 39 #include <stdio.h> 40 #include <string.h> 41 #include <unistd.h> 42 #include <limits.h> 43 #include <netdb.h> 44 45 #include "xmalloc.h" 46 #include "match.h" 47 #include "groupaccess.h" 48 #include "log.h" 49 #include "buffer.h" 50 #include "misc.h" 51 #include "servconf.h" 52 #include "key.h" 53 #include "hostfile.h" 54 #include "auth.h" 55 #include "auth-options.h" 56 #include "canohost.h" 57 #include "uidswap.h" 58 #include "packet.h" 59 #ifdef GSSAPI 60 #include "ssh-gss.h" 61 #endif 62 #include "authfile.h" 63 #include "monitor_wrap.h" 64 #include "authfile.h" 65 #include "ssherr.h" 66 #include "compat.h" 67 #include "pfilter.h" 68 69 #ifdef HAVE_LOGIN_CAP 70 #include <login_cap.h> 71 #endif 72 73 /* import */ 74 extern ServerOptions options; 75 extern int use_privsep; 76 77 /* Debugging messages */ 78 Buffer auth_debug; 79 int auth_debug_init; 80 81 #ifndef HOST_ONLY 82 /* 83 * Check if the user is allowed to log in via ssh. If user is listed 84 * in DenyUsers or one of user's groups is listed in DenyGroups, false 85 * will be returned. If AllowUsers isn't empty and user isn't listed 86 * there, or if AllowGroups isn't empty and one of user's groups isn't 87 * listed there, false will be returned. 88 * If the user's shell is not executable, false will be returned. 89 * Otherwise true is returned. 90 */ 91 int 92 allowed_user(struct passwd * pw) 93 { 94 #ifdef HAVE_LOGIN_CAP 95 extern login_cap_t *lc; 96 int match_name, match_ip; 97 char *cap_hlist, *hp; 98 #endif 99 struct ssh *ssh = active_state; /* XXX */ 100 struct stat st; 101 const char *hostname = NULL, *ipaddr = NULL; 102 int r; 103 u_int i; 104 105 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 106 if (!pw || !pw->pw_name) 107 return 0; 108 109 #ifdef HAVE_LOGIN_CAP 110 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 111 ipaddr = ssh_remote_ipaddr(ssh); 112 113 lc = login_getclass(pw->pw_class); 114 115 /* 116 * Check the deny list. 117 */ 118 cap_hlist = login_getcapstr(lc, "host.deny", NULL, NULL); 119 if (cap_hlist != NULL) { 120 hp = strtok(cap_hlist, ","); 121 while (hp != NULL) { 122 match_name = match_hostname(hostname, hp); 123 match_ip = match_hostname(ipaddr, hp); 124 /* 125 * Only a positive match here causes a "deny". 126 */ 127 if (match_name > 0 || match_ip > 0) { 128 free(cap_hlist); 129 login_close(lc); 130 return 0; 131 } 132 hp = strtok(NULL, ","); 133 } 134 free(cap_hlist); 135 } 136 137 /* 138 * Check the allow list. If the allow list exists, and the 139 * remote host is not in it, the user is implicitly denied. 140 */ 141 cap_hlist = login_getcapstr(lc, "host.allow", NULL, NULL); 142 if (cap_hlist != NULL) { 143 hp = strtok(cap_hlist, ","); 144 if (hp == NULL) { 145 /* Just in case there's an empty string... */ 146 free(cap_hlist); 147 login_close(lc); 148 return 0; 149 } 150 while (hp != NULL) { 151 match_name = match_hostname(hostname, hp); 152 match_ip = match_hostname(ipaddr, hp); 153 /* 154 * Negative match causes an immediate "deny". 155 * Positive match causes us to break out 156 * of the loop (allowing a fallthrough). 157 */ 158 if (match_name < 0 || match_ip < 0) { 159 free(cap_hlist); 160 login_close(lc); 161 return 0; 162 } 163 if (match_name > 0 || match_ip > 0) 164 break; 165 hp = strtok(NULL, ","); 166 } 167 free(cap_hlist); 168 if (hp == NULL) { 169 login_close(lc); 170 return 0; 171 } 172 } 173 174 login_close(lc); 175 #endif 176 177 #ifdef USE_PAM 178 if (!options.use_pam) { 179 #endif 180 /* 181 * password/account expiration. 182 */ 183 if (pw->pw_change || pw->pw_expire) { 184 struct timeval tv; 185 186 (void)gettimeofday(&tv, (struct timezone *)NULL); 187 if (pw->pw_expire) { 188 if (tv.tv_sec >= pw->pw_expire) { 189 logit("User %.100s not allowed because account has expired", 190 pw->pw_name); 191 return 0; /* expired */ 192 } 193 } 194 #ifdef _PASSWORD_CHGNOW 195 if (pw->pw_change == _PASSWORD_CHGNOW) { 196 logit("User %.100s not allowed because password needs to be changed", 197 pw->pw_name); 198 199 return 0; /* can't force password change (yet) */ 200 } 201 #endif 202 if (pw->pw_change) { 203 if (tv.tv_sec >= pw->pw_change) { 204 logit("User %.100s not allowed because password has expired", 205 pw->pw_name); 206 return 0; /* expired */ 207 } 208 } 209 } 210 #ifdef USE_PAM 211 } 212 #endif 213 214 /* 215 * Deny if shell does not exist or is not executable unless we 216 * are chrooting. 217 */ 218 /* 219 * XXX Should check to see if it is executable by the 220 * XXX requesting user. --thorpej 221 */ 222 if (options.chroot_directory == NULL || 223 strcasecmp(options.chroot_directory, "none") == 0) { 224 char *shell = xstrdup((pw->pw_shell[0] == '\0') ? 225 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ 226 227 if (stat(shell, &st) != 0) { 228 logit("User %.100s not allowed because shell %.100s " 229 "does not exist", pw->pw_name, shell); 230 free(shell); 231 return 0; 232 } 233 if (S_ISREG(st.st_mode) == 0 || 234 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 235 logit("User %.100s not allowed because shell %.100s " 236 "is not executable", pw->pw_name, shell); 237 free(shell); 238 return 0; 239 } 240 free(shell); 241 } 242 /* 243 * XXX Consider nuking {Allow,Deny}{Users,Groups}. We have the 244 * XXX login_cap(3) mechanism which covers all other types of 245 * XXX logins, too. 246 */ 247 248 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 249 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 250 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 251 ipaddr = ssh_remote_ipaddr(ssh); 252 } 253 254 /* Return false if user is listed in DenyUsers */ 255 if (options.num_deny_users > 0) { 256 for (i = 0; i < options.num_deny_users; i++) { 257 r = match_user(pw->pw_name, hostname, ipaddr, 258 options.deny_users[i]); 259 if (r < 0) { 260 fatal("Invalid DenyUsers pattern \"%.100s\"", 261 options.deny_users[i]); 262 } else if (r != 0) { 263 logit("User %.100s from %.100s not allowed " 264 "because listed in DenyUsers", 265 pw->pw_name, hostname); 266 return 0; 267 } 268 } 269 } 270 /* Return false if AllowUsers isn't empty and user isn't listed there */ 271 if (options.num_allow_users > 0) { 272 for (i = 0; i < options.num_allow_users; i++) { 273 r = match_user(pw->pw_name, hostname, ipaddr, 274 options.allow_users[i]); 275 if (r < 0) { 276 fatal("Invalid AllowUsers pattern \"%.100s\"", 277 options.allow_users[i]); 278 } else if (r == 1) 279 break; 280 } 281 /* i < options.num_allow_users iff we break for loop */ 282 if (i >= options.num_allow_users) { 283 logit("User %.100s from %.100s not allowed because " 284 "not listed in AllowUsers", pw->pw_name, hostname); 285 return 0; 286 } 287 } 288 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 289 /* Get the user's group access list (primary and supplementary) */ 290 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 291 logit("User %.100s from %.100s not allowed because " 292 "not in any group", pw->pw_name, hostname); 293 return 0; 294 } 295 296 /* Return false if one of user's groups is listed in DenyGroups */ 297 if (options.num_deny_groups > 0) 298 if (ga_match(options.deny_groups, 299 options.num_deny_groups)) { 300 ga_free(); 301 logit("User %.100s from %.100s not allowed " 302 "because a group is listed in DenyGroups", 303 pw->pw_name, hostname); 304 return 0; 305 } 306 /* 307 * Return false if AllowGroups isn't empty and one of user's groups 308 * isn't listed there 309 */ 310 if (options.num_allow_groups > 0) 311 if (!ga_match(options.allow_groups, 312 options.num_allow_groups)) { 313 ga_free(); 314 logit("User %.100s from %.100s not allowed " 315 "because none of user's groups are listed " 316 "in AllowGroups", pw->pw_name, hostname); 317 return 0; 318 } 319 ga_free(); 320 } 321 /* We found no reason not to let this user try to log on... */ 322 return 1; 323 } 324 325 /* 326 * Formats any key left in authctxt->auth_method_key for inclusion in 327 * auth_log()'s message. Also includes authxtct->auth_method_info if present. 328 */ 329 static char * 330 format_method_key(Authctxt *authctxt) 331 { 332 const struct sshkey *key = authctxt->auth_method_key; 333 const char *methinfo = authctxt->auth_method_info; 334 char *fp, *ret = NULL; 335 336 if (key == NULL) 337 return NULL; 338 339 if (key_is_cert(key)) { 340 fp = sshkey_fingerprint(key->cert->signature_key, 341 options.fingerprint_hash, SSH_FP_DEFAULT); 342 xasprintf(&ret, "%s ID %s (serial %llu) CA %s %s%s%s", 343 sshkey_type(key), key->cert->key_id, 344 (unsigned long long)key->cert->serial, 345 sshkey_type(key->cert->signature_key), 346 fp == NULL ? "(null)" : fp, 347 methinfo == NULL ? "" : ", ", 348 methinfo == NULL ? "" : methinfo); 349 free(fp); 350 } else { 351 fp = sshkey_fingerprint(key, options.fingerprint_hash, 352 SSH_FP_DEFAULT); 353 xasprintf(&ret, "%s %s%s%s", sshkey_type(key), 354 fp == NULL ? "(null)" : fp, 355 methinfo == NULL ? "" : ", ", 356 methinfo == NULL ? "" : methinfo); 357 free(fp); 358 } 359 return ret; 360 } 361 362 void 363 auth_log(Authctxt *authctxt, int authenticated, int partial, 364 const char *method, const char *submethod) 365 { 366 struct ssh *ssh = active_state; /* XXX */ 367 void (*authlog) (const char *fmt,...) = verbose; 368 const char *authmsg; 369 char *extra = NULL; 370 371 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 372 return; 373 374 /* Raise logging level */ 375 if (authenticated == 1 || 376 !authctxt->valid || 377 authctxt->failures >= options.max_authtries / 2 || 378 strcmp(method, "password") == 0) 379 authlog = logit; 380 381 if (authctxt->postponed) 382 authmsg = "Postponed"; 383 else if (partial) 384 authmsg = "Partial"; 385 else 386 authmsg = authenticated ? "Accepted" : "Failed"; 387 388 if ((extra = format_method_key(authctxt)) == NULL) { 389 if (authctxt->auth_method_info != NULL) 390 extra = xstrdup(authctxt->auth_method_info); 391 } 392 393 authlog("%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s", 394 authmsg, 395 method, 396 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, 397 authctxt->valid ? "" : "invalid user ", 398 authctxt->user, 399 ssh_remote_ipaddr(ssh), 400 ssh_remote_port(ssh), 401 extra != NULL ? ": " : "", 402 extra != NULL ? extra : ""); 403 404 free(extra); 405 if (!authctxt->postponed) 406 pfilter_notify(!authenticated); 407 } 408 409 void 410 auth_maxtries_exceeded(Authctxt *authctxt) 411 { 412 struct ssh *ssh = active_state; /* XXX */ 413 414 error("maximum authentication attempts exceeded for " 415 "%s%.100s from %.200s port %d ssh2", 416 authctxt->valid ? "" : "invalid user ", 417 authctxt->user, 418 ssh_remote_ipaddr(ssh), 419 ssh_remote_port(ssh)); 420 packet_disconnect("Too many authentication failures"); 421 /* NOTREACHED */ 422 } 423 424 /* 425 * Check whether root logins are disallowed. 426 */ 427 int 428 auth_root_allowed(const char *method) 429 { 430 struct ssh *ssh = active_state; /* XXX */ 431 432 switch (options.permit_root_login) { 433 case PERMIT_YES: 434 return 1; 435 case PERMIT_NO_PASSWD: 436 if (strcmp(method, "publickey") == 0 || 437 strcmp(method, "hostbased") == 0 || 438 strcmp(method, "gssapi-with-mic") == 0) 439 return 1; 440 break; 441 case PERMIT_FORCED_ONLY: 442 if (forced_command) { 443 logit("Root login accepted for forced command."); 444 return 1; 445 } 446 break; 447 } 448 logit("ROOT LOGIN REFUSED FROM %.200s port %d", 449 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 450 return 0; 451 } 452 453 454 /* 455 * Given a template and a passwd structure, build a filename 456 * by substituting % tokenised options. Currently, %% becomes '%', 457 * %h becomes the home directory and %u the username. 458 * 459 * This returns a buffer allocated by xmalloc. 460 */ 461 char * 462 expand_authorized_keys(const char *filename, struct passwd *pw) 463 { 464 char *file, ret[PATH_MAX]; 465 int i; 466 467 file = percent_expand(filename, "h", pw->pw_dir, 468 "u", pw->pw_name, (char *)NULL); 469 470 /* 471 * Ensure that filename starts anchored. If not, be backward 472 * compatible and prepend the '%h/' 473 */ 474 if (*file == '/') 475 return (file); 476 477 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 478 if (i < 0 || (size_t)i >= sizeof(ret)) 479 fatal("expand_authorized_keys: path too long"); 480 free(file); 481 return (xstrdup(ret)); 482 } 483 484 char * 485 authorized_principals_file(struct passwd *pw) 486 { 487 if (options.authorized_principals_file == NULL) 488 return NULL; 489 return expand_authorized_keys(options.authorized_principals_file, pw); 490 } 491 492 /* return ok if key exists in sysfile or userfile */ 493 HostStatus 494 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host, 495 const char *sysfile, const char *userfile) 496 { 497 char *user_hostfile; 498 struct stat st; 499 HostStatus host_status; 500 struct hostkeys *hostkeys; 501 const struct hostkey_entry *found; 502 503 hostkeys = init_hostkeys(); 504 load_hostkeys(hostkeys, host, sysfile); 505 if (userfile != NULL) { 506 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 507 if (options.strict_modes && 508 (stat(user_hostfile, &st) == 0) && 509 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 510 (st.st_mode & 022) != 0)) { 511 logit("Authentication refused for %.100s: " 512 "bad owner or modes for %.200s", 513 pw->pw_name, user_hostfile); 514 auth_debug_add("Ignored %.200s: bad ownership or modes", 515 user_hostfile); 516 } else { 517 temporarily_use_uid(pw); 518 load_hostkeys(hostkeys, host, user_hostfile); 519 restore_uid(); 520 } 521 free(user_hostfile); 522 } 523 host_status = check_key_in_hostkeys(hostkeys, key, &found); 524 if (host_status == HOST_REVOKED) 525 error("WARNING: revoked key for %s attempted authentication", 526 found->host); 527 else if (host_status == HOST_OK) 528 debug("%s: key for %s found at %s:%ld", __func__, 529 found->host, found->file, found->line); 530 else 531 debug("%s: key for host %s not found", __func__, host); 532 533 free_hostkeys(hostkeys); 534 535 return host_status; 536 } 537 538 static FILE * 539 auth_openfile(const char *file, struct passwd *pw, int strict_modes, 540 int log_missing, const char *file_type) 541 { 542 char line[1024]; 543 struct stat st; 544 int fd; 545 FILE *f; 546 547 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { 548 if (log_missing || errno != ENOENT) 549 debug("Could not open %s '%s': %s", file_type, file, 550 strerror(errno)); 551 return NULL; 552 } 553 554 if (fstat(fd, &st) < 0) { 555 close(fd); 556 return NULL; 557 } 558 if (!S_ISREG(st.st_mode)) { 559 logit("User %s %s %s is not a regular file", 560 pw->pw_name, file_type, file); 561 close(fd); 562 return NULL; 563 } 564 unset_nonblock(fd); 565 if ((f = fdopen(fd, "r")) == NULL) { 566 close(fd); 567 return NULL; 568 } 569 if (strict_modes && 570 safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) { 571 fclose(f); 572 logit("Authentication refused: %s", line); 573 auth_debug_add("Ignored %s: %s", file_type, line); 574 return NULL; 575 } 576 577 return f; 578 } 579 580 581 FILE * 582 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 583 { 584 return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); 585 } 586 587 FILE * 588 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) 589 { 590 return auth_openfile(file, pw, strict_modes, 0, 591 "authorized principals"); 592 } 593 594 struct passwd * 595 getpwnamallow(const char *user) 596 { 597 #ifdef HAVE_LOGIN_CAP 598 extern login_cap_t *lc; 599 #ifdef BSD_AUTH 600 auth_session_t *as; 601 #endif 602 #endif 603 struct ssh *ssh = active_state; /* XXX */ 604 struct passwd *pw; 605 struct connection_info *ci = get_connection_info(1, options.use_dns); 606 607 ci->user = user; 608 parse_server_match_config(&options, ci); 609 log_change_level(options.log_level); 610 process_permitopen(ssh, &options); 611 612 pw = getpwnam(user); 613 if (pw == NULL) { 614 pfilter_notify(1); 615 logit("Invalid user %.100s from %.100s port %d", 616 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 617 return (NULL); 618 } 619 if (!allowed_user(pw)) 620 return (NULL); 621 #ifdef HAVE_LOGIN_CAP 622 if ((lc = login_getclass(pw->pw_class)) == NULL) { 623 debug("unable to get login class: %s", user); 624 return (NULL); 625 } 626 #ifdef BSD_AUTH 627 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 628 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 629 debug("Approval failure for %s", user); 630 pw = NULL; 631 } 632 if (as != NULL) 633 auth_close(as); 634 #endif 635 #endif 636 if (pw != NULL) 637 return (pwcopy(pw)); 638 return (NULL); 639 } 640 641 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 642 int 643 auth_key_is_revoked(struct sshkey *key) 644 { 645 char *fp = NULL; 646 int r; 647 648 if (options.revoked_keys_file == NULL) 649 return 0; 650 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 651 SSH_FP_DEFAULT)) == NULL) { 652 r = SSH_ERR_ALLOC_FAIL; 653 error("%s: fingerprint key: %s", __func__, ssh_err(r)); 654 goto out; 655 } 656 657 r = sshkey_check_revoked(key, options.revoked_keys_file); 658 switch (r) { 659 case 0: 660 break; /* not revoked */ 661 case SSH_ERR_KEY_REVOKED: 662 error("Authentication key %s %s revoked by file %s", 663 sshkey_type(key), fp, options.revoked_keys_file); 664 goto out; 665 default: 666 error("Error checking authentication key %s %s in " 667 "revoked keys file %s: %s", sshkey_type(key), fp, 668 options.revoked_keys_file, ssh_err(r)); 669 goto out; 670 } 671 672 /* Success */ 673 r = 0; 674 675 out: 676 free(fp); 677 return r == 0 ? 0 : 1; 678 } 679 680 void 681 auth_debug_add(const char *fmt,...) 682 { 683 char buf[1024]; 684 va_list args; 685 686 if (!auth_debug_init) 687 return; 688 689 va_start(args, fmt); 690 vsnprintf(buf, sizeof(buf), fmt, args); 691 va_end(args); 692 buffer_put_cstring(&auth_debug, buf); 693 } 694 695 void 696 auth_debug_send(void) 697 { 698 char *msg; 699 700 if (!auth_debug_init) 701 return; 702 while (buffer_len(&auth_debug)) { 703 msg = buffer_get_string(&auth_debug, NULL); 704 packet_send_debug("%s", msg); 705 free(msg); 706 } 707 } 708 709 void 710 auth_debug_reset(void) 711 { 712 if (auth_debug_init) 713 buffer_clear(&auth_debug); 714 else { 715 buffer_init(&auth_debug); 716 auth_debug_init = 1; 717 } 718 } 719 720 struct passwd * 721 fakepw(void) 722 { 723 static struct passwd fake; 724 static char nouser[] = "NOUSER"; 725 static char nonexist[] = "/nonexist"; 726 727 memset(&fake, 0, sizeof(fake)); 728 fake.pw_name = nouser; 729 fake.pw_passwd = __UNCONST( 730 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"); 731 fake.pw_gecos = nouser; 732 fake.pw_uid = (uid_t)-1; 733 fake.pw_gid = (gid_t)-1; 734 fake.pw_class = __UNCONST(""); 735 fake.pw_dir = nonexist; 736 fake.pw_shell = nonexist; 737 738 return (&fake); 739 } 740 #endif 741 742 /* 743 * Returns the remote DNS hostname as a string. The returned string must not 744 * be freed. NB. this will usually trigger a DNS query the first time it is 745 * called. 746 * This function does additional checks on the hostname to mitigate some 747 * attacks on legacy rhosts-style authentication. 748 * XXX is RhostsRSAAuthentication vulnerable to these? 749 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?) 750 */ 751 752 static char * 753 remote_hostname(struct ssh *ssh) 754 { 755 struct sockaddr_storage from; 756 socklen_t fromlen; 757 struct addrinfo hints, *ai, *aitop; 758 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 759 const char *ntop = ssh_remote_ipaddr(ssh); 760 761 /* Get IP address of client. */ 762 fromlen = sizeof(from); 763 memset(&from, 0, sizeof(from)); 764 if (getpeername(ssh_packet_get_connection_in(ssh), 765 (struct sockaddr *)&from, &fromlen) < 0) { 766 debug("getpeername failed: %.100s", strerror(errno)); 767 return strdup(ntop); 768 } 769 770 debug3("Trying to reverse map address %.100s.", ntop); 771 /* Map the IP address to a host name. */ 772 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 773 NULL, 0, NI_NAMEREQD) != 0) { 774 /* Host name not found. Use ip address. */ 775 return strdup(ntop); 776 } 777 778 /* 779 * if reverse lookup result looks like a numeric hostname, 780 * someone is trying to trick us by PTR record like following: 781 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 782 */ 783 memset(&hints, 0, sizeof(hints)); 784 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 785 hints.ai_flags = AI_NUMERICHOST; 786 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 787 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 788 name, ntop); 789 freeaddrinfo(ai); 790 return strdup(ntop); 791 } 792 793 /* Names are stored in lowercase. */ 794 lowercase(name); 795 796 /* 797 * Map it back to an IP address and check that the given 798 * address actually is an address of this host. This is 799 * necessary because anyone with access to a name server can 800 * define arbitrary names for an IP address. Mapping from 801 * name to IP address can be trusted better (but can still be 802 * fooled if the intruder has access to the name server of 803 * the domain). 804 */ 805 memset(&hints, 0, sizeof(hints)); 806 hints.ai_family = from.ss_family; 807 hints.ai_socktype = SOCK_STREAM; 808 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 809 logit("reverse mapping checking getaddrinfo for %.700s " 810 "[%s] failed.", name, ntop); 811 return strdup(ntop); 812 } 813 /* Look for the address from the list of addresses. */ 814 for (ai = aitop; ai; ai = ai->ai_next) { 815 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 816 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 817 (strcmp(ntop, ntop2) == 0)) 818 break; 819 } 820 freeaddrinfo(aitop); 821 /* If we reached the end of the list, the address was not there. */ 822 if (ai == NULL) { 823 /* Address not found for the host name. */ 824 logit("Address %.100s maps to %.600s, but this does not " 825 "map back to the address.", ntop, name); 826 return strdup(ntop); 827 } 828 return strdup(name); 829 } 830 831 /* 832 * Return the canonical name of the host in the other side of the current 833 * connection. The host name is cached, so it is efficient to call this 834 * several times. 835 */ 836 837 const char * 838 auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 839 { 840 static char *dnsname; 841 842 if (!use_dns) 843 return ssh_remote_ipaddr(ssh); 844 else if (dnsname != NULL) 845 return dnsname; 846 else { 847 dnsname = remote_hostname(ssh); 848 return dnsname; 849 } 850 } 851